This invention generally relates to molding a sand mold, and in particular to a method and apparatus for compacting molding sand that is introduced into a mold space. Further, this invention also relates to a method for removing the sand mold from the mold space.
A conventional method for molding a sand mold by compacting or squeezing molding sand that is introduced into a mold space that is defined by a pattern plate, flask, and rams is known. In this method, the molding sand is compacted, while the pattern plate and the rams contact each other. Because such a method needs large cylinders for vertically moving the pattern plate, the height of a molding machine that employs them must be increased proportionately. Thus, what is needed is a means for enabling the installation of the resulting higher machine. For example, a pit should be provided on a floor.
Another conventional squeeze molding process with a leveling frame is also available. In this process, molding sand is introduced into a mold space defined by a flask, a pattern plate, and a lower auxiliary frame. Then a pressure head located at the upper position (upper head) and a lower head at the lower position (lower head), which are driven by the corresponding cylinders, compact the molding sand in the mold space. This molding process includes a method of removing a sand mold from the mold space. In this process, the lower head is lowered to remove a pattern from the sand mold, and then the upper head is lifted. The flask is then released from its fixed condition by a fixing-and-releasing mechanism. The flask, which has been used to mold the sand mold, is moved onto the following station by a conveyor. The removal of the sand mold is performed when the cylinders of the lower head are fully extended. When the pattern is removed from the sand mold, however, one problem occurs. That is, the removal of the sand mold is inaccurate. This results in the surface of the mold collapsing. Thus a faulty mold is produced.
Generally, other conventional methods of removing a sand mold also use cylinders. The removal is carried out when the cylinders are extended. Because guide pins, which are associated with the cylinders, may lack rigidity, the removal of the sand mold often fails. Unfortunately, a guide pin having a sufficient rigidity may have an increased diameter and an increased cost resulting from it.
In a conventional molding machine, to form a sand mold in a flask, molding sand is introduced into a space defined by a pattern plate, a flask, and a filling frame, where the flask and the filing frame overlap on the top of the pattern plate, and then the introduced molding sand is smoothed by scraping. A planar squeezing plate or multi-segmented squeezing feet compact the smoothed molding sand.
The smoothing of the molding sand by scraping, however, spills a relatively high amount of the molding sand. Further, with the planer squeezing plate, the compacting is not made uniform between an upper portion of a pattern of the pattern plate and a lower portion of it. In particular, the compacting of the lower portion of the pattern may be insufficient. With the multi-segmented squeezing feet, because the top surface of the sand mold as made is not planar, its rough surface must be ground after the molding process has been completed. This will result in a waste of the molding sand.
One object of the present invention provides a method and apparatus for compacting introduced molding sand in a mold space that is defined by a pattern plate, a flask, and a compacting means. The method and apparatus enable the molding sand to be generally compacted at a predetermined hardness without large cylinders (e.g., each of them has a height that needs a pit for enabling the molding machine to be installed).
Another object of the invention provides a method of removing a sand mold with a great accuracy.
Another object of the invention provides a method and apparatus for molding a sand mold where the amount of the spilled or ground molding sand is significantly reduced, all the molding sand of a sand mold is uniformly compacted, sufficient rigidity can be obtained, the sand mold can also be accurately removed, and the cost can be reduced.
One aspect of the invention provides an apparatus for introducing molding sand into a mold space in which a sand mold is produced, and for compacting the introduced molding sand in the mold space.
The apparatus includes a pattern plate having a pattern, a vertically-movable, lower auxiliary frame for surrounding the pattern plate, a vertically-movable flask, which is placed on the lower auxiliary frame in such a manner that it surrounds the pattern, a vertically-movable filling frame disposed on the flask, and a vertically-movable compacting means located above the flask in such manner that the lower portion thereof is inserted into the filling frame. The pattern plate, the lower auxiliary frame, the flask, the filling frame, and the compacting means together define a mold space. The apparatus also includes means for introducing molding sand into the mold space.
First, the compacting means is lowered in a condition where at least the lower auxiliary frame cannot be lowered, to compact the molding sand in the mold space (the first squeeze). Following the primary squeeze, the compacting means is further lowered, in a condition in which the filling frame, the lower subsidiary frame, and the flask can be made to move lower, to further compact the molding sand in the mold space (the second squeeze).
Preferably, the force of the compacting of the second squeeze is greater than that of the first squeeze.
The compacting means may be multi-segmented squeeze feet.
In the method for removing a sand mold of the invention, a mold space is defined by a horizontally fixed pattern plate having a pattern, a vertically-movable, lower auxiliary frame surrounding the pattern plate, a vertically-movable flask, which is placed above the lower auxiliary frame in such a way that it surrounds the pattern, a vertically movable filling frame placed above the flask, and a compacting means mounted on a vertically-movable supporting means that is located above the flask in such a manner that the lower portion of the compacting means is inserted into the filling frame. In this method, the compacting means provides two steps in the compacting, that is, first and second squeezes, applied to the introduced molding sand in the mold space. Then the produced sand mold is removed.
The method comprises the steps of lifting the lower auxiliary frame at a predetermined velocity to apply an upward force to the supporting means via the filling frame, while lifting a flask, in which a sand mold has been produced, the compacting means, and the filling frame, in unison, so as to separate the flask from the pattern plate, and to remove the separated flask.
The method may be applicable to a sand mold that is molded by means of an xe2x80x9caeration filling.xe2x80x9d The term xe2x80x9caerationxe2x80x9d refers herein to an action to fluidize the molding sand to be introduced into the mold space with compressed air. Further, the term xe2x80x9caeration fillingxe2x80x9d refers herein to introducing the molding sand that is floated or fluidized by the aeration into the mold space by applying more compressed air.
An apparatus for molding the sand mold of this invention includes a base having a substantially square cross section, and at least three rod-like elements standing on the base. At least two among the at least three rod-like elements are upwardly-extending cylinders, each having a piston rod. The distal ends, which include the distal ends of the piston rods of two cylinders, of the at least three rod-like elements, are attached to supporting means that can be vertically moved by driving the upwardly-extending cylinders. The supporting means supports a sand hopper for containing the molding sand. The sand hopper includes aeration means for aerating the contained molding sand with an airflow of compressed air, and a plurality of nozzles for discharging the aerated molding sand by an additional airflow of compressed air. Vertically movable, multi-segmented squeeze feet are mounted on the lower portion of the sand hopper at locations which each are adjacent to the corresponding nozzle. The apparatus also includes a vertically movable filling frame surrounding the nozzles and the squeeze feet, and pattern carrying means. The filling frame includes vent holes to vent, with the molding sand, the compressed air that is discharged from the nozzles. The pattern carrying means includes a pair of pattern carriers that each carries a pattern plate. The pattern carrying means alternately moves on and off the patterns to a location that is aligned with the filling plate above the base.
The discharged molding sand from the nozzles is introduced into a mold space defined by the pattern plate, the filing frame, and the squeeze feet. The squeeze feet then compact the molding sand.
Two of the upwardly-extending cylinders may be located on corners of one diagonal line on the base. In this case, two other upwardly-extending cylinders may be located on corners of another diagonal line on the base. That is, the four cylinders acting as the rod-like elements may be employed. Alternatively, a pair of holders, each of which has vertically slidable guide pins fitted therein, may be located on the corners of the second diagonal line on the base.
The rod-like elements may be three upwardly-extending cylinders that are arranged to form a triangle on the base. In this case, the carrying means can be a turntable that rotates around the one cylinder, which as the vertex of the triangle forms the axis of rotation.
In each embodiment, separated and vertically-movable squeeze feet may be employed. The squeeze surface that is formed by the lower ends of the squeeze feet may have a protruding or receding profile when the mold space is being formed, and may have a planer profile when the compacting is completed.